1. Field of the Invention
The present invention relates generally to self-contained or cordless tools, and more particularly to a cordless tool for driving a fastener, such as a nail, staple or the like, into a desired surface which includes an adjustable shear block assembly which can be readily manipulated by a user to accommodate fasteners of at least two different lengths so as to provide accurate guiding of the fasteners without requiring a user to connect any additional parts to the tool.
2. Description of the Related Art
An example of a cordless tool for driving fasteners is illustrated in U.S. Pat. No. Re. 32,452 which is owned by the assignee herein. That tool utilizes an internal combustion motor to drive a nail or the like into a desired surface and includes a magazine for holding a plurality of fasteners. The fasteners are typically are collated into a strip, are positioned within a feed slot or track in the magazine and are sequentially are advanced into a driving position within a bore of the tool. A shear block or guide surface is included between the magazine and the bore for separating the fastener in the bore from the adjacent fastener in the magazine and guiding the fastener in the bore as it is being driven.
Although that tool and magazine can accommodate nails of different lengths, substantially small nails can occasionally slightly tip or tumble toward the magazine feed slot as they are being driven. Such tumbling can cause inaccurate driving of the nail and possible jamming of the nail within the tool.
One way to reduce tumbling of small nails is to provide a plurality of nail head feed tracks or slots in the magazine and shear block, one each for a different length fastener. An example of such a multiple nail head feed track tool is illustrated in U.S. Pat. No. 5,005,750 which discloses a magazine and shear block having a plurality of parallel feed slots for nail heads and a separate insert strip which is inserted by a user to enable pins or brads to advance without play.
Another type of multiple feed track magazine is illustrated in U.S. Pat. No. 5,096,109 which discloses a magazine having an axial shaft including a plurality of axial grooves of various depths where the shaft is rotatable to adjust the magazine for accommodating heads of different length brads.
With both of the above referenced patents, however, the magazine is bulky and care must be taken to insure that the appropriate slot is utilized for a given nail. Additionally, the tool in both of these patents varies the point of impact with the fastener which can affect the driving of the fastener, especially with tools which provide adjustable driving depths.
Another way of reducing tumbling is to provide a separate magazine nail guide insert which can be affixed at the exit end of the magazine by a user to guide small nails as they are driven. An example of a separate nail guide is illustrated in sales brochure No. NFD842 of Senco Products, Inc., for a SN325+ Framing Nailer. Such a separate nail guide insert, however, is not permanently attached to the tool which makes it difficult to install on the job site and raises the possibility of losing the nail guide.
It therefore would be desirable to provide a magazine and shear block having a single fastener feed slot and an adjustable shear block guide surface which is permanently attached to the tool and can be readily actuated by a user to accommodate fasteners of different lengths and prevent tumbling of substantially smaller fasteners as they are being driven.